U.S. patent number 10,967,863 [Application Number 16/695,390] was granted by the patent office on 2021-04-06 for control device of vehicle.
This patent grant is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The grantee listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Akira Hino, Katsumi Kono, Masato Matsubara, Hirofumi Sato, Shojiro Suga, Hideki Takamatsu, Takaaki Tokura.
United States Patent |
10,967,863 |
Tokura , et al. |
April 6, 2021 |
Control device of vehicle
Abstract
A control device of a vehicle with a stepped automatic
transmission has: a gradient acquiring part; a driving force
calculating part; a future change estimating part; and a shift
control part. The shift control part prohibits change of the gear
stage when the speed of change of the speed or acceleration of the
vehicle in the future if the maximum driving force applied, is
within a reference range of speed of change where the occupants
would not notice a change in speed or acceleration, and permits
change of the gear stage when the speed of change of the speed or
acceleration of the vehicle in the future if the maximum driving
force applied, is outside the reference range of speed of
change.
Inventors: |
Tokura; Takaaki (Nagoya,
JP), Takamatsu; Hideki (Fujinomiya, JP),
Sato; Hirofumi (Mishima, JP), Suga; Shojiro
(Nissin, JP), Kono; Katsumi (Toyota, JP),
Hino; Akira (Toyota, JP), Matsubara; Masato
(Toyota, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota |
N/A |
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI KAISHA
(Toyota, JP)
|
Family
ID: |
1000005468041 |
Appl.
No.: |
16/695,390 |
Filed: |
November 26, 2019 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20200164876 A1 |
May 28, 2020 |
|
Foreign Application Priority Data
|
|
|
|
|
Nov 27, 2018 [JP] |
|
|
JP2018-221103 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60W
10/11 (20130101); B60W 10/06 (20130101); B60W
50/0097 (20130101); B60W 30/18 (20130101); B60W
2710/10 (20130101); B60W 2710/0666 (20130101); B60W
2520/105 (20130101); B60W 2552/15 (20200201); B60W
2556/65 (20200201) |
Current International
Class: |
B60W
30/18 (20120101); F16H 59/66 (20060101); B60W
50/00 (20060101); B60W 10/11 (20120101); B60W
10/06 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Lewis; Tisha D
Attorney, Agent or Firm: Oliff PLC
Claims
The invention claimed is:
1. A control device of a vehicle provided with a stepped automatic
transmission, configured to: acquire a gradient of a road on which
the vehicle is scheduled to drive in the future; calculate a
maximum driving force when a gear stage of the automatic
transmission is a current gear stage; estimate a change of speed or
acceleration of the vehicle in the future if the maximum driving
force is applied, based on the acquired gradient of the road and
the calculated maximum driving force; control a gear stage of the
automatic transmission; and control an output torque of an internal
combustion engine, wherein: the control device is configured to
prohibit change of the gear stage when the estimated speed of
change of the speed or acceleration of the vehicle in the future if
the maximum driving force applied, is within a reference range of
speed of change where the occupants would not notice a change in
speed or acceleration, and permit change of the gear stage when the
estimated speed of change of the speed or acceleration of the
vehicle in the future if the maximum driving force applied, is
outside the reference range of speed of change; and the control
device is configured to: calculate a current driving force when the
gear stage of the automatic transmission is the current gear stage
and the output torque of the internal combustion engine is the
current output torque; estimate a change of speed or acceleration
of the vehicle in the future when it is assumed the current driving
force continues, based on the acquired gradient of the road and the
calculated current driving force; and control the output torque so
that when the estimated speed of change of the speed or
acceleration of the vehicle in the future when assuming the current
driving force continues, is outside a minimum range of speed of
change narrower than the reference range of speed of change, the
speed of change is within the minimum range of speed of change.
2. The control device of a vehicle according to claim 1,
comprising: a communication device able to communicate with a
vehicle other than the vehicle, wherein the control device is
configured to acquire the gradient of the road on which the vehicle
is scheduled to be driven in the future from another vehicle
driving in front of the vehicle through the communication device.
Description
FIELD
The present invention relates to a control device of a vehicle.
BACKGROUND
Known in the art is a control device of a vehicle detecting a
gradient angle of a road on which a vehicle is driven, calculating
a gradient angle which a vehicle can climb based on an output
torque of an engine, a total gear ratio, and a carrying capacity of
a vehicle, and notifying that the vehicle cannot be driven up a
slope on a road if a climbable gradient angle is smaller than the
gradient angle of the road being driven on (for example, PTL
1).
CITATION LIST
Patent Literature
[PTL 1] Japanese Unexamined Patent Publication No. 2017-77765
SUMMARY
Technical Problem
In this regard, in a stepped automatic transmission of a vehicle, a
gear stage is set based on an operating state of a vehicle, such as
an amount of depression of an accelerator pedal and a speed of the
vehicle. Therefore, when the amount of depression of the
accelerator pedal is constant, if the vehicle accelerates and the
speed of the vehicle increases, the gear is automatically shifted
up in the automatic transmission. On the other hand, if the vehicle
is driven on an upward slope and the speed of the vehicle
decreases, the gear is automatically shifted down in the automatic
transmission.
For this reason, if a vehicle is driven over a bumpy road, the
speed of the vehicle will frequently change. As a result, in the
automatic transmission, the gear will be frequently shifted up and
shifted down. If the gear is repeatedly frequently shifted up and
shifted down in this way, the driveability will be
deteriorated.
In view of the above problem, an object of the present disclosure
is to keep the driveability from deteriorating due to the gear
being repeatedly frequently shifted up and shifted down by a
stepped automatic transmission.
Solution to Problem
The present invention was made so as to solve the above problem and
has as its gist the following.
(1) A control device of a vehicle provided with a stepped automatic
transmission, comprising:
a gradient acquiring part acquiring a gradient of a road on which
the vehicle is scheduled to drive in the future,
a driving force calculating part calculating a maximum driving
force when a gear stage of the automatic transmission is a current
gear stage,
a future change estimating part estimating a change of speed or
acceleration of the vehicle in the future if the maximum driving
force is applied, based on the gradient of the road acquired by the
gradient acquiring part and the maximum driving force calculated by
the driving force calculating part, and
a shift control part controlling a gear stage of the automatic
transmission, wherein
the shift control part prohibits change of the gear stage when the
speed of change of the speed or acceleration of the vehicle in the
future if the maximum driving force applied, estimated by the
future change estimating part, is within a reference range of speed
of change where the occupants would not notice a change in speed or
acceleration, and permits change of the gear stage when the speed
of change of the speed or acceleration of the vehicle in the future
if the maximum driving force applied, estimated by the future
change estimating part, is outside the reference range of speed of
change.
(2) The control device of a vehicle according to claim 1, further
comprising:
an output torque control part controlling an output torque of an
internal combustion engine,
wherein the driving force calculating part calculates a current
driving force when the gear stage of the automatic transmission is
the current gear stage and the output torque of the internal
combustion engine is the current output torque,
the future change estimating part estimates a change of speed or
acceleration of the vehicle in the future when it is assumed the
current driving force continues, based on the gradient of the road
acquired by the gradient acquiring part and the current driving
force calculated by the driving force calculating part, and
the output torque control part controls the output torque so that
when the speed of change of the speed or acceleration of the
vehicle in the future when assuming the current driving force
continues, estimated by the future change estimating part, is
outside a minimum range of speed of change narrower than the
reference range of speed of change, the speed of change is within
the minimum range of speed of change.
(3) The control device of a vehicle according to claim 1, further
comprising:
a communication device able to communicate with a vehicle other
than the vehicle,
wherein the gradient acquiring part acquires the gradient of the
road on which the vehicle is scheduled to be driven in the future
from another vehicle driving in front of the vehicle through the
communication device.
Advantageous Effects of Invention
According to the present disclosure, the drivability is kept from
deteriorating due to the gear being repeatedly frequently shifted
up and shifted down by a stepped automatic transmission.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a view schematically showing the configuration of a
vehicle mounting a control device according to a first
embodiment.
FIG. 2 is a view of the configuration schematically showing the
control device.
FIG. 3 is a functional block diagram of an ECU relating to
processing for control of the vehicle.
FIG. 4 is a view showing a relationship between a speed of the
vehicle (vehicle speed) and an amount of depression of an
accelerator pedal (accelerator opening degree), and a gear
stage.
FIG. 5 is a time chart showing trends in the vehicle speed and gear
stage when a vehicle is being driven over a road with a changing
gradient.
FIG. 6 is a time chart showing trends in the vehicle speed, jerk,
and gear stage when a vehicle is being driven over a road with a
changing gradient.
FIG. 7 is a flow chart showing shift judging processing for judging
if a gear should be shifted.
FIG. 8 is a flow chart showing shift judging processing for judging
if a gear should be shifted.
DESCRIPTION OF EMBODIMENTS
Below, referring to the drawings, embodiments of the present
invention will be explained in detail. Note that, in the following
description, similar constituent elements are assigned the same
reference signs.
First Embodiment
Configuration of Vehicle
First, referring to FIG. 1, the configuration of the vehicle 1 will
be explained. FIG. 1 is a view schematically showing the
configuration of a vehicle 1 mounting a control device according to
a first embodiment. As shown in FIG. 1, the vehicle 1 is provided
with an internal combustion engine 2, stepped automatic
transmission 3, differential gear 4, and wheels 5.
The internal combustion engine 2 is a prime mover burning fuel such
as gasoline or diesel fuel inside the engine to convert heat energy
of combustion gas to mechanical energy. The output of the internal
combustion engine 2 is controlled by adjusting the amount of fuel
and air supplied to the internal combustion engine 2.
The automatic transmission 3 is a power transmission system
transmitting power output from the internal combustion engine 2
while changing torque or speed. The automatic transmission 3 is
connected through a flywheel, etc., to a crankshaft (not shown) of
the internal combustion engine 2. Power is input from the internal
combustion engine 2 to the automatic transmission 3. On the other
hand, the automatic transmission 3 is connected through a propeller
shaft 6 to a differential gear 4 and output the power to the
differential gear 4.
The automatic transmission 3 can transmit power output from the
internal combustion engine 2 by a plurality of different gear
ratios. In this regard, the "gear ratio" means the ratio of a
rotational speed at an input side with respect to a rotational
speed of an output side. In the automatic transmission 3, the gear
ratio is automatically switched in accordance with the operating
state of the internal combustion engine.
In the present embodiment, the automatic transmission 3 has four
gear stages. Therefore, it can transmit power by four different
gear ratios. At the gear stages of the first speed gear to fourth
speed gear, the gear ratio is highest at the first speed gear and
the gear ratio is lowest at the fourth speed gear. Note that, while
the automatic transmission 3 has four gear stages in the present
embodiment, the number of stages may be any number, so long as the
automatic transmission 3 has gear stages.
The differential gear 4 is used for absorbing the difference in
rotational speeds of the left and right wheels 5 while equally
distributing the power transmitted from the automatic transmission
3 to the left and right wheels 5. The differential gear 4 transmits
the power to the left and right wheels 5 through the drive shaft
7.
Control Device
Next, referring to FIG. 2, the configuration of the control device
10 of the vehicle 1 will be explained. FIG. 2 is a view of the
configuration schematically showing the control device 10. As shown
in FIG. 2, the control device 10 is provided with an ECU 11. The
ECU 11 controls the internal combustion engine 2 and the automatic
transmission 3.
The ECU 11 has a vehicle internal communication interface 12,
memory 13, and processor 14. The vehicle internal communication
interface 12 and memory 13 are connected through signal wires to
the processor 14.
The vehicle internal communication interface 12 has an interface
circuit for connecting the ECU 3 to a vehicle internal network 15
based on the CAN (Controller Area Network) or other standard. That
is, the vehicle internal communication interface 12 is connected
through the vehicle internal network 15 to various actuators or
various sensors, which are explained later. Further, the vehicle
internal communication interface 12 receives the output data from
the various sensors and transmits the received output data to the
processor 14. Further, the vehicle internal communication interface
12 inputs the output signals transmitted from the processor 14 to
the various actuators.
The memory 13, for example, has a volatile semiconductor memory and
nonvolatile semiconductor memory. The memory 13 stores various
data, etc., used when various processing is performed by the
processor 14. For example, the memory 13 stores output data
received from the various sensors, and map information, etc.
Further, the memory 13 stores a computer program for enabling the
processor 14 to perform the various processing.
The processor 14 has one or more CPU (central processing units) and
their peripheral circuits. The processor 14 may further have a GPU
(graphics processing unit). The processor 14 performs the later
explained shift judging processing at every certain time interval
and controls the actuators of the automatic transmission 3 based on
the results of shift judging processing, while the ignition switch
of the vehicle 1 is on.
In the present embodiment, the control device 10 is further
provided with engine actuators 21, a transmission actuator 31,
accelerator sensor 41, vehicle speed sensor 42, torque sensor 43,
weight sensor 44, vehicle external communication device 51, and GPS
receiver 52. These actuators, sensors, vehicle external
communication device 51, and GPS receiver 52 are connected through
the vehicle internal network 15 to the vehicle internal
communication interface 12 of the ECU 11.
The engine actuators 21 are various actuators for controlling the
internal combustion engine 2. The engine actuators 21 include, for
example, a fuel feed system feeding fuel to combustion chambers of
the internal combustion engine 2, an opening degree control device
controlling an opening degree of a throttle valve provided in an
engine intake passage, and spark plugs igniting an air-fuel mixture
in the combustion chambers of the internal combustion engine 2.
Therefore, the engine actuators 21 can adjust the output torque of
the internal combustion engine 2.
The transmission actuator 31 includes a solenoid driving a brake
mechanism or clutch mechanism, which control rotation of a ring
gear, pinion gear, and sun gear provided in the automatic
transmission 3. Therefore, the transmission actuator 31 can change
the gear stage of the automatic transmission 3.
The accelerator sensor 41 is attached to the accelerator pedal and
detects the amount of depression of the accelerator pedal. The
vehicle speed sensor 42 is attached, for example, to the wheels 5
or the drive shaft 7, and detects the speed of the vehicle 1. The
torque sensor 43, for example, is attached to the output shaft of
the internal combustion engine 2 or the automatic transmission 3
(crankshaft or propeller shaft), and detects the output torque of
the internal combustion engine 2 or the automatic transmission 3.
The weight sensor 44 is attached, for example, to the suspension of
the vehicle 1, and detects the weight of the vehicle 1. The outputs
of these sensors are input to the ECU 11 through the vehicle
internal network 15.
The vehicle external communication device 51 is a device able to
communicate wirelessly with an external server or with another
vehicle. The standard used in the wireless communication includes
the Long Term Evolution (LTE) formulated by the 3GPP, the wireless
LAN (IEEE 802.11a/b/g/n/ac), Mobile WiMAX (IEEE 802.16e), iBurst or
WAVE(IEEE 802.20), DSRC (Dedicated Short Range Communication), or
various other communication standards. The vehicle external
communication device 51 sends and receives signals to and from the
ECU 11 through the vehicle internal network 15.
The GPS receiver 52 is a device for receiving signals from three or
more GPS satellites and detecting the current position of the
vehicle 1 (for example, the latitude and longitude of the vehicle
1). The GPS receiver 52 sends the detected current position
information of the vehicle 1 to the ECU 11.
Processing at ECU
FIG. 3 is a functional block diagram of an ECU 3 relating to
processing for control of the vehicle. The ECU 3 has a gradient
acquiring part 61, driving force calculating part 62, future change
estimating part 63, shift control part 64, and output torque
control part 65. These functional blocks of the ECU 3 are, for
example, functional modules realized by a computer program
operating on the processor 14. Note that, these functional blocks
may also be dedicated processing circuits provided at the processor
14.
The gradient acquiring part 61 acquires the gradient of a road on
which the vehicle 1 is scheduled to be driven in the future. In
particular, the gradient acquiring part 61 acquires the gradient of
the road scheduled to be driven on within the nearest predetermined
time in the road of the driving route on which the vehicle 1 is
scheduled to be driven in the future.
The gradient acquiring part 61 acquires the gradient of the road,
for example, based on the current position information of the
vehicle 1 transmitted from the GPS receiver 52 and the map
information stored in the memory 13. In this case, the map
information includes the gradient information of roads. The
gradient acquiring part 61 identifies the road on which the vehicle
is scheduled to be driven in the future (for example, the road on
which it is scheduled to be driven within the next 10 seconds or
the road within 1 km from the current position scheduled to be
driven on in the future), based on the current position information
transmitted from the GPS receiver 52 and the preset driving route.
Then, the gradient acquiring part 61 acquires the gradient of the
road on which the vehicle is scheduled to be driven in the future,
from the map information stored in the memory 13.
In this case, the ECU 3 may be configured to update the map
information stored in the memory 13 through the vehicle external
communication device 51 at any timing. Specifically, if the map
information of the external server (not shown) is updated, the
updated map information is sent from the server to the vehicle
external communication device 51, and the map information stored in
the memory 13 is updated to the sent map information.
The map information of the external server may be automatically
updated by the gradient information sent from a vehicle being
driven over a covered road. In this case, the vehicle driving over
the covered road for example, calculates the gradient .theta. of
the road using the following equation (1):
.theta.=arcsin[(Fd-Ma-F(Av.sup.2+Bv+C))/Mg] (1)
In the equation (1), Fd indicates the driving force output by the
vehicle, M indicates the total weight of the vehicle, "a" is the
acceleration of the vehicle, F is the driving resistance when
assuming the gradient is 0, "v" is the speed of the vehicle, and
"g" is the acceleration of gravity. Further, A, B, and C are
constants calculated by computation or experiments.
The driving force Fd is calculated, for example, based on the
amount of depression of the accelerator pedal, the gear stage of
the automatic transmission 3, etc. The total weight M of the
vehicle is calculated, for example, based on the weight sensor 44,
etc., provided at the suspension of the vehicle. The acceleration
"a" of the vehicle is, for example, calculated based on the output
of the vehicle speed sensor 42. In addition, the driving resistance
F is calculated in advance by experiments or by computation for
each car model.
The vehicle being driven on the covered road calculates, by the ECU
3, the gradient of the road, using the above equation (1), based on
the driving force Fd, the total weight M of the vehicle, the
acceleration "a" of the vehicle, and the driving resistance F.
Then, the vehicle sends the gradient information of the road being
driven on, to the server together with the position information.
The server updates the map information based on the gradient
information and the position information sent from vehicles being
driven through various positions in this way.
Note that, in the present embodiment, the gradient information of
roads calculated by vehicles is sent to the server, map information
updated based on this gradient information is sent to the vehicles,
and, at the vehicles, the gradient of the road on which the vehicle
is scheduled to be driven in the future is acquired based on the
map information. However, the vehicles may also be configured to
directly receive gradient information on the road on which the
vehicle 1 is to be driven in the future, together with position
information, from other vehicles in the surroundings being driven
in front of the vehicle 1. In this case, the gradient acquiring
part 61 acquires the gradient of the road on which the vehicle is
scheduled to be driven in the future, based on the gradient
information and the position information received from other
vehicles, in addition to the road on which the vehicle 1 is
scheduled to be driven in the future and the map information stored
in memory 13.
The driving force calculating part 62 calculates the driving force
of the vehicle 1 when the gear stage of the automatic transmission
3 is the current gear stage. The driving force calculating part 62
estimates, in particular, a maximum driving force when the gear
stage of the automatic transmission 3 is the current gear stage. In
addition, the driving force calculating part 62 calculates the
current driving force when the gear stage of the automatic
transmission is the current gear stage and the output torque of the
internal combustion engine 2 is the current output torque.
The driving force of the vehicle 1 when the amount of depression of
the accelerator pedal is maximum (that is, when the output of the
internal combustion engine 2 is maximum) changes in accordance with
the gear stage of the automatic transmission 3 and the speed of the
vehicle 1. The maximum driving force means the largest driving
force able to be output by the vehicle 1 when changing the speed of
the vehicle 1 at the gear stage of the automatic transmission 3.
The relationship between the gear stages and the maximum driving
force is calculated in advance by experiments or by computation and
stored in the memory 13. The driving force calculating part 62
calculates the maximum driving force, based on the current gear
stage of the automatic transmission 3, using the relationship
stored in the memory 13.
On the other hand, the driving force of the vehicle 1 changes
depending also on the amount of depression of the accelerator
pedal, in addition to the gear stage of the automatic transmission
3 and the speed of the vehicle 1. In the present embodiment, the
relationship between the gear stages and the driving force and the
amount of depression of the accelerator pedal is calculated in
advance by experiments or by computation and stored in the memory
13. The driving force calculating part 62 calculates the drive
force (current driving force) at the time of the current amount of
depression of the accelerator pedal, using the relationship stored
in the memory 13, based on the amount of depression of the
accelerator pedal output by the accelerator sensor 41 and the
current gear stage of the automatic transmission 3.
The future change estimating part 63 estimates the change of the
acceleration "a" of the vehicle 1 in the future when the maximum
driving force continues, based on the gradient of the road acquired
by the gradient acquiring part 61 and the maximum driving force
calculated by the driving force calculating part 62. The
acceleration "a" of the vehicle 1 at the time "t" is, for example,
calculated by the following equation (2):
a=[Fdm-F(Av.sup.2+Bv+C)-Mgsin.theta.]/M (2)
Here, Fdm indicates the maximum driving force output by the vehicle
1. The value calculated by the driving force calculating part 62 is
assigned to Fdm. Further, .theta. indicates the gradient of the
road. The value acquired by the gradient acquiring part 61 is
assigned to .theta..
In particular, in the present embodiment, the current acceleration
"a" is calculated by the above equation (2), based on the current
speed of the vehicle 1 detected by the vehicle speed sensor 42.
Further, the speed of the vehicle 1 after the fine time .DELTA.t
seconds is calculated based on the current acceleration "a"
calculated in this way, and the road (position) on which the
vehicle 1 will be driven after the fine time .DELTA.t seconds is
calculated based on the current speed. After that, the gradient of
the road on which the vehicle 1 will be driven after .DELTA.t
seconds is calculated from the gradient of the road acquired by the
gradient acquiring part 61, and the acceleration "a" after .DELTA.t
seconds is calculated based on the calculated gradient of the road
and the speed after .DELTA.t seconds. By repeating this operation,
the change in the acceleration of the vehicle 1 from the current
time to a predetermined time later (for example, 10 seconds) is
estimated.
In addition, in the present embodiment, the future change
estimating part 63 estimates the speed of change of the
acceleration, that is, the "jerk". Specifically, the jerk at the
time "t" is calculated as the difference between the acceleration
a(t) at the time "t" and the acceleration a(t+1) at the time
t+1.
The shift control part 64 controls the gear stage of the automatic
transmission 3. In the present embodiment, the shift control part
64 basically sets the gear stage, based on the current speed of the
vehicle 1 detected by the vehicle speed sensor 42 and the amount of
depression of the accelerator pedal (accelerator opening degree)
detected by the accelerator sensor 41.
FIG. 4 is a view showing a relationship between the speed of the
vehicle 1 (vehicle speed) and the amount of depression of the
accelerator pedal (accelerator opening degree) and gear stage. As
shown in FIG. 4, the gear stage is set to a higher stage as the
speed of the vehicle 1 increases. Further, the gear stage is set to
a lower stage as the amount of depression of the accelerator pedal
increases.
For example, consider the case where the speed of the vehicle 1 and
the amount of depression of the accelerator pedal change from the
values shown at s1 in FIG. 4 to the values shown at s2 in FIG. 4
with the amount of depression of the accelerator pedal maintained
constant as is and the speed becoming faster. Here, s1 is within
the region where the gear stage is set to the 2nd speed gear and s2
is within the region where the gear stage is set to the 3rd speed
gear. Therefore, in this case, the gear stage of the automatic
transmission 3 is shifted from 2nd speed gear to 3rd speed
gear.
On the other hand, consider the case where the speed of the vehicle
1 and the amount of depression of the accelerator pedal change from
the values shown at s3 in FIG. 4 to the values shown at s4 in FIG.
4 with the amount of depression of the accelerator pedal maintained
constant as is and the speed becoming slower. Here, s3 is within
the region where the gear stage is set to 3rd speed gear and s4 is
within the region where the gear stage is set to 2nd speed gear,
therefore in this case, the gear stage of the automatic
transmission 3 is shifted from 2nd speed gear to 3rd speed
gear.
The output torque control part 65 controls the output torque of the
internal combustion engine 2. The output torque control part 65
basically controls the output torque, based on the amount of
depression of the accelerator pedal detected by the accelerator
sensor 41. The output torque control part 65 basically controls the
output torque so that the output torque of the internal combustion
engine 2 is maintained constant when the gear stage of the
automatic transmission 3 is the same and the amount of depression
is being maintained constant. On the other hand, the output torque
control part 65 controls the output torque so that the output
torque of the internal combustion engine 2 becomes larger when the
amount of depression changes to become larger, while conversely so
that the output torque of the internal combustion engine 2 becomes
smaller when the amount of depression changes to become
smaller.
Frequency of Changing Gear Stage
In this regard, if the vehicle 1 is being driven on a road with a
changing gradient, the speed of the vehicle 1 will change according
to the change of the gradient. Along with this, the gear stage will
frequently change in some cases. This will be explained referring
to FIG. 5.
FIG. 5 is a time chart showing trends in the vehicle speed and gear
stage, when the vehicle 1 is being driven on a road with a changing
gradient. The example shown in FIG. 5 shows the case where the
amount of depression of the accelerator pedal for example remains a
constant full open.
As shown in FIG. 5, between the timings t0 to t2, the vehicle 1 is
driven over a road with a large gradient. For this reason, the
speed of the vehicle 1 is slow and accordingly the gear stage is
set to a low gear stage of 2nd speed gear, based on the map shown
in FIG. 4. After that, between the timings t2 to t4, the vehicle 1
is driven on a road with a small gradient (including downward
gradient). For this reason, the speed of the vehicle 1 is fast and
accordingly the gear stage is set to a high gear stage of 3rd speed
gear, based on the map shown in FIG. 4.
After that, between the timings t4 to t6, the vehicle 1 is driven
on a road with a large gradient and, between the timings t6 to t8,
is driven on a road with a small gradient. As a result, the gear
stage of the automatic transmission 3 is set to 2nd speed gear
between the timings t4 to t6, and to 3rd speed gear between the
timings t6 to t8. If alternately driving on a road with a large
gradient and a road with a small gradient in this way, in the
automatic transmission 3, the gear is repeatedly frequently shifted
up and shifted down. As a result, the drivability is
deteriorated.
On the other hand, if restricting shifting of the automatic
transmission 3 in order to suppress frequent shifting of the gear
up and shifting of the gear down in the automatic transmission 3,
the speed or acceleration of the vehicle 1 changes so much as to
make the occupants of the vehicle 1 feel uncomfortable. As a
result, the comfort of the occupants is lost.
Control of Gear Level
Therefore, in the present embodiment, the shift control part 64 is
configured so as to prohibit change of the gear stage, when the
speed of change of the acceleration of the vehicle in the future if
the maximum driving force is applied, estimated by the future
change estimating part 63, is within the reference range of speed
of change where the occupants will not notice the change of
acceleration. In addition, the shift control part 64 is configured
so as to permit the change of the gear stage, when the speed of
change of acceleration of the vehicle in the future if the maximum
driving force is applied, estimated by the future change estimating
part 63, is outside the reference range of speed of change.
Here, according to research of the inventors of the present
application, it was discovered that occupants of the vehicle 1 feel
that acceleration is constant, not when the acceleration of the
vehicle 1 is constant, but when the acceleration of the vehicle 1
changes in accordance with certain set rules. Furthermore, the
inventors of the present application discovered that when the
acceleration of the vehicle 1 is in the relationship shown by the
following equation (3), the occupants of the vehicle 1 feel that
the vehicle 1 is accelerating (or decelerating) by constants
acceleration. a(t)=.alpha.exp(-.beta.v(t)) (3)
In equation (3), a(t) is the acceleration of the vehicle 1 at the
time "t", while v(t) is the speed of the vehicle 1 at the time "t".
Further, .alpha. and .beta. are constants.
Here, assigning a(t)=dv(t)/dt and simplifying the equation,
equation (3) is expressed as the following equation (4). In the
case of integrating the both sides of the following equation (4)
and simplifying the equation, equation (4) is expressed as the
following equation (5):
.times..times..function..beta..function..alpha..times..function..beta..ti-
mes..function..alpha..beta. ##EQU00001##
Here, assuming the speed v(t) of the vehicle 1 is zero at the
timing "t"=0, the result becomes .alpha..beta.t.sub.0=1, therefore
equation (5) is expressed as the following equation (6). Further,
by differentiating both sides of equation (6), equation (7) is
derived. In the case of further differentiating both sides of
equation (7), equation (8) is derived. Note that, in equation (8),
J(t) indicates jerking. Further, equation (9) is derived from
equation (7) and equation (8).
.times..times..function..beta..times..alpha..beta..function..alpha..alpha-
..beta..function..alpha..beta..alpha..beta..function..beta..function.
##EQU00002##
As explained above, equation (3) shows the relationship between the
speed and acceleration at which occupants of the vehicle 1 feel a
vehicle is accelerating (or decelerating) by a constant
acceleration, therefore equation (9) shows the relationship between
the acceleration and jerk at which occupants of the vehicle 1 feel
a vehicle is accelerating (or decelerating) by a constant
acceleration. Therefore, when the current acceleration is a(t), if
the acceleration changes by the speed of change of acceleration
(jerk) shown by equation (9), the occupants of the vehicle 1 will
feel the acceleration is not changing.
Further, the inventors of the present application discovered that
when the jerk of the vehicle 1 is within a certain range centered
about the jerk J(t) calculated by the above equation (9) (below,
referred to as the "reference range of speed of change"), the
occupants of the vehicle 1 will not notice a change of
acceleration. Specifically, the reference range of speed of change
is, for example, shown by the following equation (10):
-.beta.a(t).sup.2-P .ltoreq.J(t).ltoreq.-.beta.a(t).sup.2+P
(10)
In equation (10), P is a positive constant and is found by
experiments. There are individual differences in the range where
the occupants will not notice a change in acceleration of the
vehicle 1, therefore P is set to a value at which most occupants
will not notice the change.
Here, as explained above, the future change estimating part 63
estimates the change of the acceleration "a" of the vehicle 1 in
the future if the maximum driving force is applied. Therefore, the
future change estimating part 63 estimates the trend in the
acceleration "a" of the vehicle 1 from the current time to a
predetermined time later (for example, 10 seconds later), and
estimates the trend in the jerk J from the trend in the
acceleration "a".
The shift control part 64 judges if the jerk J at different points
of time from the current time to a predetermined time later,
estimated by the future change estimating part 63, is within the
reference range of speed of change shown by the above equation
(10). Further, in the shift control part 64, the gear stage is
maintained when the jerk J at the different points of time is
within the reference range of speed of change, even when the gear
should be shifted in the automatic transmission 3 if referring to
the map shown in FIG. 4, since the occupants will not notice the
change of acceleration.
On the other hand, the shift control part 64 permits the change of
the gear stage when the jerk J at the different points of time is
outside the reference range of speed of change, since unless
shifting, the acceleration will change to an extent which the
occupants notice. Therefore, when sometimes the jerk J will become
a value outside the reference range of speed of change in the
period from the current time to a predetermined time later, the
gear will be shifted in accordance with the map shown in FIG. 4. As
a result, the gear stage is shifted to a suitable gear stage,
therefore the change of acceleration of the vehicle 1 is kept
within the reference range of speed of change. Therefore, when the
jerk J at the different points of time is outside the reference
range of speed of change, the shift control part 64 changes the
gear stage so that the speed of change of the acceleration of the
vehicle in the future is within the reference range of speed of
change.
FIG. 6 is a time chart showing trends in the vehicle speed, jerk,
and gear stage when the vehicle 1 is being driven over a road with
a changing gradient. In particular, FIG. 6 shows the trends in the
case where the vehicle 1 is being driven over a road having a
change of gradient similar to the example shown in FIG. 5.
The broken line X at the top in the jerk of FIG. 6 indicates
-.beta.a(t).sup.2+P. The broken line Y of the bottom indicates
-.beta.a(t).sup.2-P. Therefore, the region surrounded by the top
and bottom broken lines indicates the reference range of speed of
change. In the example shown in FIG. 6, the jerk is expected to be
maintained in the reference range of speed of change over the time
period from the timing t0 to the timing t11. As a result, in the
example shown in FIG. 6, despite the speed of the vehicle 1
changing in the same way as the example shown in FIG. 5, the gear
stage of the automatic transmission 3 is maintained at 3rd speed
gear.
Specific Control
FIG. 7 is a flow chart showing shift judging processing for judging
if a gear should be shifted. The illustrated control routine is
performed every certain time interval.
First, at step S11, the gradient acquiring part 61 acquires the
gradient of the road on which the vehicle 1 is scheduled to be
driven in the future. Specifically, the gradient acquiring part 61
identifies the road on which the vehicle 1 is scheduled to be
driven in the future based on the driving route of the vehicle 1
set in advance and the current position information sent by the GPS
receiver 52. In addition, the gradient acquiring part 61 acquires
the gradient at the road on which the vehicle is scheduled to be
driven in the future, from the map information, etc.
Next, at step S12, the driving force calculating part 62 calculates
the maximum driving force of the vehicle 1. The maximum driving
force of the vehicle 1 is calculated based on the information of
the current gear stage of the automatic transmission 3 (for
example, the command values to the automatic transmission 3).
Next, at step S13, the future change estimating part 63 estimates
the acceleration v(t) of the vehicle 1 in the future and the future
change of the acceleration a(t) and jerk J(t), in the case where
the driving force of the vehicle 1 is maintained at the maximum
driving force at the current gear stage. Specifically, the
acceleration at the different timings "t" is calculated based on
the above equation (2), and the speed v(t) at the different timings
"t" is calculated based on the calculated acceleration a(t) and the
current speed v(t). Further, the jerk J(t) at the different timings
"t" is calculated by finding the change along with time of the
acceleration calculated in this way.
Next, at step S14, the shift control part 64 judges if the gear is
expected to be shifted if the amount of depression of the
accelerator pedal is maintained constant as it is, based on the
future speed v(t) estimated by the future change estimating part 63
at step S13 and the map shown in FIG. 4. For example, if the future
speed "v" estimated by the future change estimating part 63 changes
from the speed of S3 to S4 of FIG. 4, it is judged that the gear is
expected to be shifted. If at step S14 it is judged that gear is
not expected to be shifted, the control routine is ended. On the
other hand, if, at step S14, it is judged that the gear is expected
to be shifted, the control routine proceeds to step S15.
At step S15, it is judged if the future jerk J(t) estimated by the
future change estimating part 63 at step S13 is within the
reference range of speed of change shown in the above equation
(10). If, at step S15, it is judged that the future jerk J(t) is
within the reference range of speed of change, the control routine
proceeds to step S16. At step S16, shift at the automatic
transmission 3 is prohibited, and the control routine is ended.
On the other hand, if, at step S15, it is judged that the future
jerk J(t) will be outside the reference range of speed of change,
the control routine proceeds to step S17. At step S17, shift of the
automatic transmission 3 is permitted. Therefore, when the speed of
the vehicle 1 changes so as to straddle the boundary line between
the gear stages of FIG. 4, the gear is shifted at the automatic
transmission 3.
Effects
According to the present embodiment, when the occupants are
expected to not notice the change in acceleration, shift of the
automatic transmission 3 is prohibited. For this reason, even when
driving on a road with a changing gradient so that the gear is
frequently repeatedly shifted up and shifted down by a stepped
automatic transmission, when the occupants are expected to not
notice the change in acceleration, shift of the gear is prohibited.
As a result, the comfort of the occupants is maintained, while
deterioration of the driveability due to the shift of gear being
frequently repeated is suppressed.
Modification
Note that, in the above embodiment, the shift control part 64
decides whether to permit a shift of gear, based on whether the
occupants would notice the change in acceleration of the vehicle 1.
However, the shift control part 64 may also decide whether to
permit a shift of gear, based on whether the occupants would notice
the change in the speed of the vehicle 1. In this case, the future
change estimating part 63 estimates the change of the speed of the
vehicle in the future if the maximum driving force is applied,
based on the gradient of the road acquired by the gradient
acquiring part 61 and the maximum driving force calculated by the
driving force calculating part 62. In addition, in this case, the
shift control part 64 prohibits change of the gear stage when the
speed of change of the speed of the vehicle in the future if the
maximum driving force applied, estimated by the future change
estimating part 63, is within a reference range of speed of change
where the occupants would not notice a change in speed, and permits
change of the gear stage when the speed of change of the speed of
the vehicle in the future if the maximum driving force applied,
estimated by the future change estimating part 63, is outside a
reference range of speed of change.
Second Embodiment
Next, referring to FIG. 8, a control device according to a second
embodiment will be explained. Below, parts different from the
control device according to the first embodiment will be focused on
in the explanation.
In this regard, as explained above, when the acceleration changes
to become the acceleration shown in the above-mentioned equation
(3), the occupants of the vehicle 1 feel the acceleration is
constant. On the other hand, if the amount of depression of the
accelerator pedal is maintained constant, the driver expects that
the vehicle 1 will accelerate (or decelerate) by constant
acceleration. Therefore, if the amount of depression of the
accelerator pedal is maintained constant, the vehicle 1 preferably
accelerates (or decelerates) by the acceleration shown in equation
(3).
However, on a road where the gradient continuously changes in small
extents, the actual acceleration of the vehicle 1 also changes
along with the gradient. As a result, even if the amount of
depression of the accelerator pedal is maintained constant, the
acceleration of the vehicle 1 changes becoming faster or slower
relative to the acceleration shown in equation (3).
Therefore, in the present embodiment, the driving force calculating
part 62 is configured so as to calculate the current driving force
when the gear stage of the automatic transmission 3 is the current
gear stage and the output torque of the internal combustion engine
2 is the current output torque. In addition, the future change
estimating part 63 is configured to estimate the change of
acceleration of the vehicle 1 in the future when assuming the
current driving force continues, based on the gradient of the road
acquired by the gradient acquiring part 61 and the current driving
force calculated by the driving force calculating part 62. Further,
the output torque control part 65 controls the output torque so
that when the speed of change of the acceleration of the vehicle 1
in the future when assuming the current driving force estimated by
the future change estimating part 63 continues, is outside the
minimum range of speed of change narrower than the reference range
of speed of change, the speed of change is within the minimum range
of speed of change.
Below, the control of the output torque in the output torque
control part 65 will be explained in detail. As explained above, if
the jerk of the vehicle 1 is in the relationship shown by the above
equation (9), the occupants of the vehicle 1 feel the vehicle 1 is
accelerating (or decelerating) by constant acceleration. Therefore,
if maintaining the jerk of the vehicle 1 near the value calculated
by the above equation (9), the occupants of the vehicle 1 feel the
vehicle 1 is accelerating (or decelerating) by constant
acceleration.
Therefore, in the present embodiment, the output torque control
part 65 controls the output torque of the vehicle 1 so that the
jerk of the vehicle 1 is maintained within a certain range centered
about the jerk J(t) calculated by the above equation (9) (below,
referred to as the "minimum range of speed of change"), when the
amount of depression of the accelerator pedal is maintained
constant. Here, the "minimum range of speed of change" is a range
narrower than the reference range of speed of change in the
above-mentioned first embodiment.
Specifically, using the future change estimating part 63, the
change of the acceleration a' of the vehicle 1 in the future when
the current driving force continues, is estimated based on the
gradient of the road acquired by the gradient acquiring part 61 and
the current driving force calculated by the driving force
calculating part 62. The acceleration a' of the vehicle 1 at the
timing "t" is, for example, calculated by the following equation
(11): a'=[Fdc-F(Av.sup.2+Bv+C)-Mgsin.theta.]/M (11)
In equation (11), Fdc indicates the driving force currently output
by the vehicle 1, that is, the driving force at the time of the
current amount of depression of the accelerator pedal. The current
amount of driving calculated by the driving force calculating part
62 is assigned to Fdc.
Further, the future change estimating part 63 of the present
embodiment, in the same way as the first embodiment, repeatedly
calculates the speed and acceleration of the vehicle 1 a fine time
.DELTA.t seconds later to thereby estimate the change of the
acceleration of the vehicle 1 from the current time to a
predetermined time later. In addition, the future change estimating
part 63 estimates the change of the jerk J' when assuming the
current drive force continues from the calculated change of the
acceleration "a".
The output torque control part 65 judges if the jerk of the vehicle
1 at different points of time from the current time to a
predetermined time later when assuming that the current driving
force estimated by the future change estimating part 63 continues,
is within the minimum range of speed of change shown by the
following equation (12):
-.beta.a'(t).sup.2-Q.ltoreq.J'(t).ltoreq.-.beta.a'(t).sup.2+Q
(12)
In equation (12), Q is a positive constant and is found by
experiments. Note that however, Q is a value smaller than the
constant P at the above-mentioned equation (10).
Further, the output torque control part 65 maintains the output
torque of the internal combustion engine 2 as it is without
changing it, if judging the jerk of the vehicle 1 at different
points of time from the current time to a predetermined time later
is within the minimum range of speed of change shown by the above
equation (12). On the other hand, the output torque control part 65
changes the output torque of the internal combustion engine 2, even
if the amount of depression of the accelerator pedal is constant,
if judging that at least part of the jerk of the vehicle 1 at
different points of time from the current time to a predetermined
time later is outside the minimum range of speed of change shown by
the above equation (12). For example, if the jerk of the vehicle 1
is smaller than the minimum range of speed of change, the output
torque control part 65 changes the output torque of the internal
combustion engine 2 to become larger. On the other hand, when the
jerk of the vehicle 1 is larger than the minimum range of speed of
change, the output torque control part 65 changes the output torque
of the internal combustion engine 2 to become smaller.
FIG. 8 is a flow chart showing shift judging processing for judging
if a gear should be shifted. The illustrated control routine is
performed every certain time interval. Note that, steps S21 to S27
of FIG. 8 are similar to steps S11 to S17 of FIG. 7, therefore
explanations will be omitted.
If, at step S25, it is judged that a future jerk J(t) is in the
reference range of speed of change, the control routine proceeds to
step S26 where the shift at the automatic transmission 3 is
prohibited. Next, step S28, it is judged if the future jerk J'(t)
when assuming that the current driving force continues, is within
the minimum range of speed of change shown in the above equation
(12). If at step S28 it is judged that the future jerk J'(t) is
within the minimum range of speed of change, the control routine is
ended without the output torque being adjusted. On the other hand,
if, at step S28, it is judged that the future jerk J'(t) is outside
the minimum range of speed of change, the routine proceeds to step
S29. At step S29, even if the amount of depression of the
accelerator pedal is constant, the output torque of the internal
combustion engine 2 is adjusted.
According to the second embodiment, so long as the amount of
depression of the accelerator pedal is constant, the change of
acceleration of the vehicle 1 is maintained near a range at which
occupants feel the acceleration is constant. Therefore, the
occupants are kept from feeling frequent acceleration and
deceleration, and the comfort of the occupants is improved.
Modification
Note that, in the above second embodiment, the output torque
control part 65 controls the output torque so that the occupants
feel that the acceleration of the vehicle 1 is constant. However,
the output torque control part 65 may also control the output
torque so that the occupants feel the speed of the vehicle 1 is
constant. In this case, the future change estimating part 63 is
configured to also estimate the change of speed of the vehicle 1 in
the future when assuming the current driving force continues, based
on the gradient of the road acquired by the gradient acquiring part
61 and the current driving force calculated by the driving force
calculating part 62. In addition, in this case, the output torque
control part 65 controls the output torque so that when the speed
of change of the speed of the vehicle in the future when assuming
the current driving force estimated by the future change estimating
part 63 continues, is outside a minimum range of speed of change
narrower than the reference range of speed of change, the speed of
change is within the minimum range of speed of change.
REFERENCE SIGNS LIST
1. vehicle 2. internal combustion engine 3. automatic transmission
10. control device 11. electronic control unit (ECU) 41.
accelerator sensor 42. vehicle speed sensor 43. torque sensor 44.
weight sensor 51. vehicle external communication device 52. GPS
receiver
* * * * *